It is well known to make polyalphaolefins by reacting 1-decene with boron trifluoride and butanol. The oligomer product is a mixture of dimer, trimer, and higher molecular weight materials.
The market for the trimer and higher molecular weight materials is well established, both in military applications and in automotive and industrial uses that require a 4 centistoke (cSt) or greater kinematic viscosity. The dimer, which has a viscosity of about 2 cSt, was usually recycled to the reaction. That resulted in better economics but a somewhat poorer product performance. Because of the market demand for the trimer and higher molecular weight materials and lack of market demand for dimer production, most of the work in this area has involved minimizing the amount of dimers made.
The dimer is useful in heat transfer fluids, dielectric fluids, and lubricating fluids. Recently, it also has been found to be useful in drilling fluids. This involves replacing petroleum fractions, chiefly diesel oil, in oil-based drilling fluids with environmentally compatible polyalphaolefins. Oil-based drilling fluids are undesirable in off-shore petroleum exploration because those fluids produce an unwanted sheen on the water and are harmful to certain marine life. This new market for dimers has changed the economics of the industry. Now, there is an economic motivation to increase dimer yield, rather than minimize it.
U.S. Pat. No. 5,068,487 by Theriot discloses a process for producing oligomerization of olefins with boron trifluoride and alcohol alkoxylates to produce predominately dimer and trimer. Unfortunately, this process can create a highly viscous emulsion layer in the reactant and aqueous wash streams. These emulsions can cause operating difficulties, such as inhomogeneity in the reactor, process line plugging, poor product recovery, and lengthy phase separation times.
Previously, we filed an application U.S. Ser. No. 08/217,265 to the use of boron trifluoride in conjunction with hydroxy carbonyls. In one embodiment of that invention, a ketone was used as a copromoter with the hydroxy carbonyl to improve dimer yield.
U.S. Pat. No. 4,436,947 by Morganson et al. discloses oligomerization of C.sub.6 -C.sub.20 olefins, such as 1-decene, with boron trifluoride and a mixture of an aliphatic alcohol, an aliphatic ketone, and a polyol to increase the trimer to tetramer ratio. The dimer to trimer and higher oligomer ratio of the examples varies from 0.09:1 to 0.19:1.
U.S. Pat. Nos. 4,436,947 and 5,068,487 are hereby incorporated by reference for all purposes.